基于STL模型的渐进成形支撑体的离散化设计

Discrete design of incremental forming support-body based on STL model

板料数控渐进成形中不同成形角位置的厚度不同,简单利用零件曲面或者等距偏置无法保证得到工具头与支撑体的合理间隙。利用渐进成形厚度减薄余弦定理δ=δ0cosθ,将加工件的表面离散为STL模型,提取STL各三角面片顶点坐标,x、y坐标保持不变,z坐标在Z轴负向偏置一个原始板材厚度,偏置后保持三角片拓扑关系不变,在此基础上生成支撑体表面模型。该方法依据零件模型不同成形角部位的厚度变化规律,可以得到合理的加工间隙。选择球冠型零件进行实验,获得了较好的加工件表面质量,对成形零件变形区厚度进行了测量,并对所得数据进行分析。

Because the part thickness of different forming angles in Incremental Sheet Forming （ISF） is various, a reasonable clearance between the forming tool and the support body cannot be determined by the part surface or the whole offset directly. According to the ISF thickness thinning cosine theorem δ= δ0 cos θ, the curved surface of the forming part was discretized into STL model, and then each triangle vertex coordinate value of STL model was read out, namely, x and y remained the same, and z was offset to an original plate thickness in the Z axis negative direction, but the topology relationship of the triangle was kept after vertex coordinate value offset. Therefore, based on the offset model, the curved surface of the support body was generated. According to the variation of the thickness of parts in different forming angles, a reasonable forming clearance between the forming tool and support body was obtained. The typical spherical parts were chosen to finish the forming experiment and then the ideal surface quality was obtained. The thickness value of the forming parts was measured and analyzed finally.